Last week, I ordered the most expensive material for my entire cob house: the EPDM pond liner for my (soon-coming) living roof. EPDM is a synthetic, petroleum-based rubber product commonly used for living roofs, due to its strength and durability. Apparently, it can last 50 years exposed to the sun, and presumably longer buried under dirt.
I have not been thrilled by the prospect of purchasing this petro product for my house (it’s one of the few new, synthetic materials in the whole building); however, it has been challenging to find information on building a living roof using natural materials. Apparently, Norwegians have historically used birch bark as their impermeable membrane. Getting more information than just that has proved difficult, and still, I probably wouldn’t have been willing to experiment with my first house, considering just how important a good roof is. I want to do this right. Perhaps I’ll experiment with an all-natural living roof on a different building in the future. (If anyone out there has details on any books, etc. with information on traditional living roofs, let me know!)
Anyway, the 35’x35′ sheet of EPDM cost a whopping $622, at least $100 of which was the shipping cost. The thing weighs 380 pounds. I’m pretty daunted by the idea of somehow getting this whole thing unrolled over the roof… but I’m sure with enough hands, it won’t be so bad!